The invention relates to a device for through-flowing continuous heat treatment of textile material, fleece, or paper in web form, with a permeable drum that is subjected to suction and has bottoms on the ends as a transport element, said drum being covered on its circumference by a covering that is perforated or in the form of a sieve, with sheet metal strips permanently attached to the bottoms extending from one bottom to another between the bottoms of the drum, with the lateral extent of said strips being in the radial direction.
A device of this type is known from DE 38 21 330 A1. It has the advantage that it is optimally permeable to air without the stability of the drum being reduced thereby. Another advantage is the bolted design implemented in this device. Without having to resort to the previously known welded construction, all drum jacket elements are thus permanently attached to one another by the bolted rib connections through the connecting ribs that run in the circumferential direction over the drum with the sheet metal strips that extend lengthwise across the drum. The changes in structure in the metal, which are so disadvantageous when the welded seams that are otherwise necessary are produced, are avoided in this bolted construction.
Regardless of whether the drum jacket design is welded or created by the bolted connections, the connection of the sheet metal strips to the bottoms of the drum, in other words firstly to one bottom and secondly with the nozzle star through which the fan subjects the interior of the drum to suction, is exposed during use to the higher thermal stresses encountered in practice. The bottoms have a greater heat capacity than the sheet metal strips. When a cold material enters the heated drum housing, the sheet metal strips cool off suddenly on contact with the material but initially the bottoms do not, so that there are considerable stresses in the material that lead to cracks or dents in the drum. This occurs independently of the drum design, i.e. regardless of whether it is welded or bolted.